Global System for Mobile Communications (GSM) General Packet Radio Service (GPRS) is intended to allow a service subscriber the ability to send and receive data in an end-to-end packet transfer mode without utilizing network resources in the circuit-switched mode. GPRS permits efficient use of radio and network resources when data transmission characteristics are i) packet based, ii) intermittent and non-periodic, iii) possibly frequent, with small transfers of data, e.g. less than 500 octets, or iv) possibly infrequent, with large transfers of data, e.g. more than several hundred kilobytes. User applications may include Internet browsers, electronic mail and so on.
The European Telecommunications Standards Institute (ETSI) GSM specifications define what is referred to as a "mobile station class" for GPRS mobile stations. The mobile station class specifies some of the behavior to which a mobile station must conform regarding its operation in packet mode, circuit-switched mode, or both packet and circuit-switched mode. For example, one such mobile station class is a Class A mobile station which supports simultaneous attachment, monitoring, activation, invocation and traffic flow on both circuit-switched voice and packet-switched data services. On the other hand, a Class B mobile station has been defined to support only simultaneous attachment, monitoring and activation on both circuit-switched voice and packet-switched data services, with invocation and traffic flow possible on either service on a mutually exclusive basis. Finally, a Class C mobile station is defined to support only non-simultaneous attach, i.e. mutually exclusive attach, on either circuit-switched voice or packet-switched data services.
Mobile station classes may also be assigned, or changed, in some cases by the user, subject to limitations such as manufacturer's options and equipment limitations. For example, a user application may have the ability to issue a command to change the mobile station class of the subscriber equipment currently in use. The mobile station classes are therefore to be treated as "effective" classes, as users may exercise some control over mobile station class identity.
One of the problems associated with providing a Class A capable mobile station is that two receivers and two transmitters are required, along with a combiner/duplexer, interface to a common Subscriber Identity Module (SIM) card and possibly an additional call processor, depending upon the number of embedded user-level applications desired to coexist during circuit-switched voice and packet-switched data service operation. This presents the need among mobile station manufacturers to develop a whole new architecture for such equipment, resulting in an increased cost of the device.
As illustrated in FIG. 1, in a known fixed allocation of an existing GPRS/EDGE medium access control operation, a signaling flow is such that a timeslot allocation bitmap is sent from the network to a physical layer 100, or layer 1. A medium access controller 110 recognizes an address, and a radio link controller 120 assembles a control message. A radio resource layer 130 sends a bitmap of when to transmit to the medium access controller 110, which transmits GPRS/EDGE data to the physical layer 100. On the other hand, in dynamic allocation of a known existing GPRS/EDGE medium access control operation, a signaling flow is such that a control packet is sent to a physical layer 140 of a mobile station, and a medium access controller 150 decodes and recognizes an address or an uplink state flag (USF), giving the mobile station the right to transmit in the TDMA frame, so that GPRS/EDGE data is transmitted to the physical layer 140.
Since there has typically been a large impact of the service on both the mobile station and base station signaling, in addition to there being certain technical problems associated with the approach, attempts at designing a simplified Class A mobile station service have proven to be inefficient. For example, the manner in which the existing medium access control (MAC) method for GPRS on a dedicated channel is utilized, in the presence of another dedicated channel to carry voice information in the usual manner, would allow the mobile station to be handed over in two different directions, i.e. the circuit-switched voice call may have been handed to another GSM cell while the packet switched data transfer may have remained in the old cell, or possibly have been forced to reselect to a cell different from the one on which the circuit-switched voice call resides. This may require the mobile station to support the simultaneous reception of two RF channels, which is beyond the scope of a simplified simultaneous voice/data service.
Accordingly, what is needed is a simplified method for allowing simultaneous circuit-switched voice and GPRS data interchange to occur using current mobile station hardware architecture.